TUESDAY, April 9 (HealthDay News) -- Daughters born to women who had excess levels of estrogen during pregnancy may be at increased risk for
breast cancer, a new study suggests.

That's because high estrogen levels in the womb can disable the powerful breast cancer tumor suppressor gene BRCA1 in daughters, the researchers at Georgetown Lombardi Comprehensive Cancer Center said in a Georgetown news release.

Their study of 1-year-old girls whose mothers had high estrogen levels during pregnancy also found that the daughters had other gene abnormalities that can contribute to the risk of breast cancer and breast cancer recurrence.

This includes a gene defect in the so-called unfolded protein response pathway, which has been linked to breast cancer risk and resistance to the breast cancer drug tamoxifen.

Although the study found an association between high estrogen levels in pregnancy and factors that raise breast cancer risk in daughters, it did not prove cause and effect.

If the findings are confirmed, they could be used to identify women at increased risk for breast cancer and to lower their risk before the disease develops, the researchers said.

There are drugs available that may make it "possible to reverse the increase in breast cancer risk and prevent development of resistance to tamoxifen in these women," study lead author Leena Hilakivi-Clarke, a professor of oncology at Georgetown Lombardi, said in the news release.

The study was to be presented Tuesday at the American Association for Cancer Research annual meeting, in Washington, D.C. The data and conclusions of research presented at meetings are typically considered preliminary until published in a peer-reviewed medical journal.